As Jim K suggested in another thread, better than weld the oil squirter hole in the rod (which can cause an important strenght loss due to the change of crystalline properties of the rod material in the weld point and surroundings) it is better to fill and close it with epoxi resine for metal.
I'm not sure that all 24 valve engines are fitted with oil squirters in the block, I think this feature was introduced in the 24V besides the chain driven oil pump and the belt tensioner installed in the place of the oil pump-distrubutor toothed pulley (there are also 12V with squirters in the block)
. So it is important to check if your engine has this feature.
I suppose the THS rod profile doesn't differ so much compared to the original Alfa rod, in any case I think it can be take some material from the block or liner without problems, I have seen many liners with machined neck lines for the rods.
About rev limit, I have no information, but I suppose 7500-8000 could begin to be potentially dangerous.
Paco